1. Field of the Invention
This invention relates to a process for the production of an alkyl polyglycoside. More specifically, the present invention relates to a process for the production of an alkyl polyglycoside having improved color properties.
2. Description of the Related Art
Alkyl polyglycosides are glucose ethers wherein the anomeric alcohol group is replaced by an alkoxy group. Some of the glucose moieties are oligomerized such that a typical alkyl polyglycoside sample is comprised of a mixture of isomeric monoglycosides, diglycosides, triglycosides, etc., with each higher oligomer present in decreasing amounts. Alkyl polyglycosides have an average degree of oligomerization (DP) of from 1.4 to 1.7 units of glucose. Alkyl polyglycosides are conveniently prepared by reacting an alcohol of the type and chain length which is desired to form the "alkyl" portion of the glycoside of interest with a saccharide reactant (e.g., a monosaccharide such as glucose, xylose, arabinose, galactose, fructose, etc., or a polysaccharide such as starch, hemicellulose, lactose, maltose, melibiose, etc.) or with a glycoside starting material wherein the aglycone portion thereof is different from the alkyl substituent desired for the ultimate alkyl glycoside product of interest. Typically, such reaction is carried out under conditions wherein the alcohol is present in a mole ratio of alcohol/glucose in the range of from 2.0 to 5.0, at an elevated temperature and in the presence of an acid catalyst. The product contains alkyl polyglycoside and excess alcohol which is normally removed by distilling the alcohol from the alkyl polyglycoside product. Because the alcohol distillation operation requires temperatures in excess of 150.degree. C., thermal degradation of the alkyl polyglycoside normally takes place and produces an undesirable color in the product. The alcohol-free alkyl polyglycoside product is then normally subjected to one or more decolorization operations wherein the product is reacted with hydrogen peroxide or a Group I or Group II metal borohydride to remove any color bodies which may have been formed during the prior process steps such as the alcohol removal operation.
The shorter the time period that the alkyl polyglycoside product is exposed to the elevated temperatures required for efficient alcohol removal the less pronounced is the color development and the simpler the subsequent decolorization process becomes.